[BL] Move GitSHA1 and Configure.h into BuildInfo.

All info is collected in BaseLib/BuildInfo.{h,cpp} and in the BaseLib::BuildInfo
namespace.

QT4_FOUND is now added to the compiler flags and not defined in Configure.h.

Unused definitions were collected by GC.
Remove OGS_BUILD_INFO, which is always generated.
Merge pull request #442 from endJunction/GitInfoVersion

Safe git version information (the c++ part).